【单选题】

From childhood to old age, we all use language as a means of broadening our knowledge of ourselves and the world about us. When humans first (61) , they were like newborn children, unable to use this (62) tool. Yet once language developed, the possibilities for human kind’s future (63) and cultural growth increaseD、

Many linguists believe that evolution is (64) for our ability to produce and use language. They (65) that our highly evolved brain provides us (66) an innate language ability not found in lower (67) . Proponents of this innateness theory say that our (68) for language is inborn, but that language itself develops gradually, (69) a function of the growth of the brain during childhooD、Therefore there are critical (70) times for language development.
Current (71) of innateness theory are mixed, however, evidence supporting the existence of some innate abilities is undeniable. (72) , more and more schools are discovering that foreign languages are best taught in (73) grades. Young children often can learn several languages by being (74) to them, while adults have a much harder time learning another language once the (75) of their first language have become firmly fixeD、
A．various
B．different
C．the higher
D．the lower